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Liu P, Zhao W, Liu Z, Pan Y, Duan D, Cui T. High-temperature superconductivities and crucial factors influencing the stability of LaThH 12 under moderate pressures. Phys Chem Chem Phys 2024; 26:8237-8246. [PMID: 38385503 DOI: 10.1039/d3cp05408j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2024]
Abstract
The recent discovery of high-temperature superconductivity in compressed hydrides has reignited the long-standing quest for room-temperature superconductors. However, the synthesis of superconducting hydrides under moderate pressure and the identification of crucial factors that affect their stability remain challenges. Here, we predicted the ternary clathrate phases of LaThH12 with potential superconductivity under high pressures and specifically proposed a novel R3̄c-LaThH12 phase exhibiting a remarkable Tc of 54.95 K at only 30 GPa to address these confusions. Our first-principles studies show that the high-Tc value of Pm3̄m and Cmmm-LaThH12 phases was induced by the strong electron-phonon coupling driven by the synergy of the electron-phonon matrix element and phonon softening caused by Fermi surface nesting. Importantly, we demonstrate the dual effects of enhanced ionic bonding and expanded orbital hybridization between Th-6f and H-sp3 orbitals during depressurization are primary factors governing the dynamic stability of R3̄c-LaThH12 at low pressures. Our findings offer crucial insights into the underlying mechanisms governing low-pressure stability and provide guidance for experimental efforts aimed at realizing hydrogen-based superconductors with both low synthesis pressures and high-Tc.
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Affiliation(s)
- Pengye Liu
- Institute of High Pressure Physics, School of Physical Science and Technology, Ningbo University, Ningbo, 315211, People's Republic of China.
| | - Wendi Zhao
- Institute of High Pressure Physics, School of Physical Science and Technology, Ningbo University, Ningbo, 315211, People's Republic of China.
| | - Zhao Liu
- Institute of High Pressure Physics, School of Physical Science and Technology, Ningbo University, Ningbo, 315211, People's Republic of China.
| | - Yilong Pan
- Institute of High Pressure Physics, School of Physical Science and Technology, Ningbo University, Ningbo, 315211, People's Republic of China.
| | - Defang Duan
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun, 130012, People's Republic of China
| | - Tian Cui
- Institute of High Pressure Physics, School of Physical Science and Technology, Ningbo University, Ningbo, 315211, People's Republic of China.
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun, 130012, People's Republic of China
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Record high Tc element superconductivity achieved in titanium. Nat Commun 2022; 13:5411. [PMID: 36109496 PMCID: PMC9478155 DOI: 10.1038/s41467-022-33077-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Accepted: 08/29/2022] [Indexed: 11/08/2022] Open
Abstract
It is challenging to search for high Tc superconductivity (SC) in transition metal elements wherein d electrons are usually not favored by conventional BCS theory. Here we report experimental discovery of surprising SC up to 310 GPa with Tc above 20 K in wide pressure range from 108 GPa to 240 GPa in titanium. The maximum Tconset above 26.2 K and zero resistance Tczero of 21 K are record high values hitherto achieved among element superconductors. The Hc2(0) is estimated to be ∼32 Tesla with coherence length 32 Å. The results show strong s-d transfer and d band dominance, indicating correlation driven contributions to high Tc SC in dense titanium. This finding is in sharp contrast to the theoretical predications based on pristine electron-phonon coupling scenario. The study opens a fresh promising avenue for rational design and discovery of high Tc superconductors among simple materials via pressure tuned unconventional mechanism. Superconductivity at megabar pressures has recently attracted interest in the context of hydrides. Here, the authors demonstrate superconductivity up to 26 K at high pressure in elemental titanium, and further suggest that electron correlations contribute to the high Tc.
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Kurzhals P, Kremer G, Jaouen T, Nicholson CW, Heid R, Nagel P, Castellan JP, Ivanov A, Muntwiler M, Rumo M, Salzmann B, Strocov VN, Reznik D, Monney C, Weber F. Electron-momentum dependence of electron-phonon coupling underlies dramatic phonon renormalization in YNi 2B 2C. Nat Commun 2022; 13:228. [PMID: 35017477 PMCID: PMC8752669 DOI: 10.1038/s41467-021-27843-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Accepted: 12/16/2021] [Indexed: 11/09/2022] Open
Abstract
Electron-phonon coupling, i.e., the scattering of lattice vibrations by electrons and vice versa, is ubiquitous in solids and can lead to emergent ground states such as superconductivity and charge-density wave order. A broad spectral phonon line shape is often interpreted as a marker of strong electron-phonon coupling associated with Fermi surface nesting, i.e., parallel sections of the Fermi surface connected by the phonon momentum. Alternatively broad phonons are known to arise from strong atomic lattice anharmonicity. Here, we show that strong phonon broadening can occur in the absence of both Fermi surface nesting and lattice anharmonicity, if electron-phonon coupling is strongly enhanced for specific values of electron-momentum, k. We use inelastic neutron scattering, soft x-ray angle-resolved photoemission spectroscopy measurements and ab-initio lattice dynamical and electronic band structure calculations to demonstrate this scenario in the highly anisotropic tetragonal electron-phonon superconductor YNi2B2C. This new scenario likely applies to a wide range of compounds.
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Affiliation(s)
- Philipp Kurzhals
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76021, Karlsruhe, Germany
| | - Geoffroy Kremer
- Département de Physique and Fribourg Center for Nanomaterials, Université de Fribourg, 1700, Fribourg, Switzerland
| | - Thomas Jaouen
- Département de Physique and Fribourg Center for Nanomaterials, Université de Fribourg, 1700, Fribourg, Switzerland
- Univ Rennes, CNRS, IPR (Institut de Physique de Rennes) - UMR 6251, F-35000, Rennes, France
| | - Christopher W Nicholson
- Département de Physique and Fribourg Center for Nanomaterials, Université de Fribourg, 1700, Fribourg, Switzerland
| | - Rolf Heid
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76021, Karlsruhe, Germany
| | - Peter Nagel
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76021, Karlsruhe, Germany
| | - John-Paul Castellan
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76021, Karlsruhe, Germany
- Laboratoire Léon Brillouin (CEA-CNRS), CEA Saclay, F-91911, Gif-sur-Yvette, France
| | - Alexandre Ivanov
- Institut Laue-Langevin, 71 avenue des Martyrs CS 20156, 38042, Grenoble Cedex 9, France
| | - Matthias Muntwiler
- Paul Scherrer Institut, Swiss Light Source, 5232, Villigen PSI, Switzerland
| | - Maxime Rumo
- Département de Physique and Fribourg Center for Nanomaterials, Université de Fribourg, 1700, Fribourg, Switzerland
| | - Bjoern Salzmann
- Département de Physique and Fribourg Center for Nanomaterials, Université de Fribourg, 1700, Fribourg, Switzerland
| | - Vladimir N Strocov
- Paul Scherrer Institut, Swiss Light Source, 5232, Villigen PSI, Switzerland
| | - Dmitry Reznik
- Department of Physics, University of Colorado at Boulder, Boulder, CO, 80309, USA
- Center for Experiments on Quantum Materials, University of Colorado at Boulder, Boulder, CO, 80309, USA
| | - Claude Monney
- Département de Physique and Fribourg Center for Nanomaterials, Université de Fribourg, 1700, Fribourg, Switzerland
| | - Frank Weber
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76021, Karlsruhe, Germany.
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Majumdar A, Tse JS, Yao Y. Mechanism for the Structural Transformation to the Modulated Superconducting Phase of Compressed Hydrogen Sulfide. Sci Rep 2019; 9:5023. [PMID: 30903002 PMCID: PMC6430777 DOI: 10.1038/s41598-019-41607-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Accepted: 03/13/2019] [Indexed: 12/03/2022] Open
Abstract
A comprehensive description of crystal and electronic structures, structural transformations, and pressure-dependent superconducting temperature (Tc) of hydrogen sulfide (H2S) compressed from low pressure is presented through the analysis of the results from metadynamics simulations. It is shown that local minimum metastable crystal structures obtained are dependent on the choice of pressure-temperature thermodynamic paths. The origin of the recently proposed 'high-Tc' superconducting phase with a modulated structure and a diffraction pattern reproducing two independent experiments was the low pressure Pmc21 structure. This Pmc21 structure is found to transform to a Pc structure at 80 K and 80 GPa which becomes metallic and superconductive above 100 GPa. This structure becomes dynamically unstable above 140 GPa beyond which phonon instability sets in at about a quarter in the Γ to Y segment. This explains the transformation to a 1:3 modulation structure at high pressures proposed previously. The pressure trend of the calculated Tc for the Pc structure is consistent with the experimentally measured 'low-Tc phase'. Fermi surface analysis hints that pressurized hydrogen sulfide may be a multi-band superconductor. The theoretical results reproduced many experimental characteristics, suggesting that the dissociation of H2S is unrequired to explain the superconductivity of compressed H2S at any pressure.
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Affiliation(s)
- Arnab Majumdar
- Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5E2, Canada
| | - John S Tse
- Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5E2, Canada.
| | - Yansun Yao
- Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5E2, Canada.
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5
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Yue SY, Cheng L, Liao B, Hu M. Electron–phonon interaction and superconductivity in the high-pressure cI16 phase of lithium from first principles. Phys Chem Chem Phys 2018; 20:27125-27130. [DOI: 10.1039/c8cp05455j] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Superconductivity in different phases of lithium (Li) under high pressure has been widely studied. Here, we study the electron–phonon interaction and superconductivity in one interesting high-pressure phase of Li (cI16) between 45 GPa and 76 GPa.
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Affiliation(s)
- Sheng-Ying Yue
- Aachen Institute for Advanced Study in Computational Engineering Science (AICES)
- RWTH Aachen University
- 52062 Aachen
- Germany
- Department of Mechanical Engineering
| | - Long Cheng
- Institute of Mineral Engineering
- Division of Materials Science and Engineering
- Faculty of Georesources and Materials Engineering
- RWTH Aachen University
- 52064 Aachen
| | - Bolin Liao
- Department of Mechanical Engineering
- University of California
- Santa Barbara
- USA
| | - Ming Hu
- Aachen Institute for Advanced Study in Computational Engineering Science (AICES)
- RWTH Aachen University
- 52062 Aachen
- Germany
- Institute of Mineral Engineering
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6
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Arita R, Koretsune T, Sakai S, Akashi R, Nomura Y, Sano W. Nonempirical Calculation of Superconducting Transition Temperatures in Light-Element Superconductors. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29. [PMID: 28060417 DOI: 10.1002/adma.201602421] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Revised: 08/05/2016] [Indexed: 02/05/2023]
Abstract
Recent progress in the fully nonempirical calculation of the superconducting transition temperature (Tc ) is reviewed. Especially, this study focuses on three representative light-element high-Tc superconductors, i.e., elemental Li, sulfur hydrides, and alkali-doped fullerides. Here, it is discussed how crucial it is to develop the beyond Migdal-Eliashberg (ME) methods. For Li, a scheme of superconducting density functional theory for the plasmon mechanism is formulated and it is found that Tc is dramatically enhanced by considering the frequency dependence of the screened Coulomb interaction. For sulfur hydrides, it is essential to go beyond not only the static approximation for the screened Coulomb interaction, but also the constant density-of-states approximation for electrons, the harmonic approximation for phonons, and the Migdal approximation for the electron-phonon vertex, all of which have been employed in the standard ME calculation. It is also shown that the feedback effect in the self-consistent calculation of the self-energy and the zero point motion considerably affect the calculation of Tc . For alkali-doped fullerides, the interplay between electron-phonon coupling and electron correlations becomes more nontrivial. It has been demonstrated that the combination of density functional theory and dynamical mean field theory with the ab initio downfolding scheme for electron-phonon coupled systems works successfully. This study not only reproduces the experimental phase diagram but also obtains a unified view of the high-Tc superconductivity and the Mott-Hubbard transition in the fullerides. The results for these high-Tc superconductors will provide a firm ground for future materials design of new superconductors.
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Affiliation(s)
- Ryotaro Arita
- RIKEN Center for Emergent Matter Science, Wako, Saitama, 351-0198, Japan
- JST ERATO Isobe Degenerate π-Integration Project, Advanced Institute for Materials Research, Tohoku University, Katahira, Aoba-ku, Sendai, 980-8577, Japan
| | - Takashi Koretsune
- RIKEN Center for Emergent Matter Science, Wako, Saitama, 351-0198, Japan
- JST-PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan
| | - Shiro Sakai
- RIKEN Center for Emergent Matter Science, Wako, Saitama, 351-0198, Japan
| | - Ryosuke Akashi
- Department of Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Yusuke Nomura
- Centre de Physique Théorique, École Polytechnique, CNRS, Université Paris-Saclay, F-91128, Palaiseau, France
| | - Wataru Sano
- RIKEN Center for Emergent Matter Science, Wako, Saitama, 351-0198, Japan
- Department of Applied Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
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7
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Abstract
At room environment, all materials can be classified as insulators or metals or in-between semiconductors, by judging whether they are capable of conducting the flow of electrons. One can expect an insulator to convert into a metal and to remain in this state upon further compression, i.e., pressure-induced metallization. Some exceptions were reported recently in elementary metals such as all of the alkali metals and heavy alkaline earth metals (Ca, Sr, and Ba). Here we show that a compound of CLi4 becomes progressively less conductive and eventually insulating upon compression based on ab initio density-functional theory calculations. An unusual path with pressure is found for the phase transition from metal to semimetal, to semiconductor, and eventually to insulator. The Fermi surface filling parameter is used to describe such an antimetallization process.
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8
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Schaeffer AM, Cai W, Olejnik E, Molaison JJ, Sinogeikin S, dos Santos AM, Deemyad S. Boundaries for martensitic transition of (7)Li under pressure. Nat Commun 2015; 6:8030. [PMID: 26271453 PMCID: PMC4557344 DOI: 10.1038/ncomms9030] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Accepted: 07/07/2015] [Indexed: 12/02/2022] Open
Abstract
Physical properties of lithium under extreme pressures continuously reveal unexpected features. These include a sequence of structural transitions to lower symmetry phases, metal-insulator-metal transition, superconductivity with one of the highest elemental transition temperatures, and a maximum followed by a minimum in its melting line. The instability of the bcc structure of lithium is well established by the presence of a temperature-driven martensitic phase transition. The boundaries of this phase, however, have not been previously explored above 3 GPa. All higher pressure phase boundaries are either extrapolations or inferred based on indirect evidence. Here we explore the pressure dependence of the martensitic transition of lithium up to 7 GPa using a combination of neutron and X-ray scattering. We find a rather unexpected deviation from the extrapolated boundaries of the hR3 phase of lithium. Furthermore, there is evidence that, above ∼3 GPa, once in fcc phase, lithium does not undergo a martensitic transition. Lithium metal under extreme pressures shows a sequence of structural phase transitions. Here, the authors use neutron scattering and X-ray diffraction techniques under high pressure to expand the experimental phase diagram of lithium, showing an unexpected deviation from existing boundaries.
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Affiliation(s)
- Anne Marie Schaeffer
- Department of Physics and Astronomy, University of Utah, 115S 1400E, Salt Lake City, Utah 84112, USA
| | - Weizhao Cai
- Department of Physics and Astronomy, University of Utah, 115S 1400E, Salt Lake City, Utah 84112, USA
| | - Ella Olejnik
- Department of Physics and Astronomy, University of Utah, 115S 1400E, Salt Lake City, Utah 84112, USA
| | - Jamie J Molaison
- Quantum Condensed Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Stanislav Sinogeikin
- HPCAT, Geophysical Laboratory, Carnegie Institution of Washington, Argonne, Illinois 60439, USA
| | - Antonio M dos Santos
- Quantum Condensed Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Shanti Deemyad
- Department of Physics and Astronomy, University of Utah, 115S 1400E, Salt Lake City, Utah 84112, USA
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9
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High-pressure superconducting phase diagram of 6Li: isotope effects in dense lithium. Proc Natl Acad Sci U S A 2014; 112:60-4. [PMID: 25538300 DOI: 10.1073/pnas.1412638112] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We measured the superconducting transition temperature of (6)Li between 16 and 26 GPa, and report the lightest system to exhibit superconductivity to date. The superconducting phase diagram of (6)Li is compared with that of (7)Li through simultaneous measurement in a diamond anvil cell (DAC). Below 21 GPa, Li exhibits a direct (the superconducting coefficient, α, T(c) proportional M(-α), is positive), but unusually large isotope effect, whereas between 21 and 26 GPa, lithium shows an inverse superconducting isotope effect. The unusual dependence of the superconducting phase diagram of lithium on its atomic mass opens up the question of whether the lattice quantum dynamic effects dominate the low-temperature properties of dense lithium.
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10
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Akashi R, Arita R. Development of density-functional theory for a plasmon-assisted superconducting state: application to lithium under high pressures. PHYSICAL REVIEW LETTERS 2013; 111:057006. [PMID: 23952436 DOI: 10.1103/physrevlett.111.057006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2013] [Indexed: 06/02/2023]
Abstract
We extend the density-functional theory for superconductors (SCDFT) to take account of the dynamical structure of the screened Coulomb interaction. We construct an exchange-correlation kernel in the SCDFT gap equation on the basis of the random-phase approximation, where electronic collective excitations such as plasmons are properly treated. Through an application to fcc lithium under high pressures, we demonstrate that our new kernel gives higher transition temperatures (T(c)) when the plasmon and phonon cooperatively mediate pairing and it improves the agreement between the calculated and experimentally observed T(c). The present formalism opens the door to nonempirical studies on unconventional electron mechanisms of superconductivity based on density-functional theory.
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Affiliation(s)
- Ryosuke Akashi
- Department of Applied Physics, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
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11
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Yao Y, Klug DD. Pressure induced dimer to ionic insulator and metallic structural changes in Al2Br6. J Chem Phys 2013; 138:094501. [PMID: 23485307 DOI: 10.1063/1.4793314] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
High-pressure phase transitions in Al2Br6 were theoretically investigated using first principles density functional methods. A structural transformation from the initial molecular solid phase to a planar polymeric phase is predicted near 0.4 GPa that is accompanied with a substantial volume drop. A unique feature of this phase transition is that the hcp lattice of Br atoms remains unchanged during the transition, whereas the Al atoms are displaced from the original tetrahedral sites to the octahedral sites. The calculated phonon spectra indicate that the predicted phase is mechanically stable at 1 atm, and therefore it may be quench-recovered to ambient conditions and exist as a metastable form. A second structural transformation is predicted to occur at around 80 GPa, and also at this point, the AlBr3 reaches a metallic state. The electronic structure of the metallic phase features soft phonon modes and Fermi surface nesting in the Brillouin zone, which leads to localized electron-phonon coupling. By comparing with the experimental data available for high-pressure BI3, the superconducting critical temperature Tc for the metallic phase of AlBr3 is estimated to be at 0.5 K or above.
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Affiliation(s)
- Yansun Yao
- Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5E2, Canada.
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12
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Schwarz U, Wosylus A, Rosner H, Schnelle W, Ormeci A, Meier K, Baranov A, Nicklas M, Leipe S, Müller CJ, Grin Y. Dumbbells of Five-Connected Silicon Atoms and Superconductivity in the Binary Silicides MSi3 (M = Ca, Y, Lu). J Am Chem Soc 2012; 134:13558-61. [DOI: 10.1021/ja3055194] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ulrich Schwarz
- Max-Planck-Institut für Chemische Physik fester Stoffe, 01187 Dresden, Germany
| | - Aron Wosylus
- Max-Planck-Institut für Chemische Physik fester Stoffe, 01187 Dresden, Germany
| | - Helge Rosner
- Max-Planck-Institut für Chemische Physik fester Stoffe, 01187 Dresden, Germany
| | - Walter Schnelle
- Max-Planck-Institut für Chemische Physik fester Stoffe, 01187 Dresden, Germany
| | - Alim Ormeci
- Max-Planck-Institut für Chemische Physik fester Stoffe, 01187 Dresden, Germany
| | - Katrin Meier
- Max-Planck-Institut für Chemische Physik fester Stoffe, 01187 Dresden, Germany
| | - Alexey Baranov
- Max-Planck-Institut für Chemische Physik fester Stoffe, 01187 Dresden, Germany
| | - Michael Nicklas
- Max-Planck-Institut für Chemische Physik fester Stoffe, 01187 Dresden, Germany
| | - Susann Leipe
- Max-Planck-Institut für Chemische Physik fester Stoffe, 01187 Dresden, Germany
| | - Carola J. Müller
- Max-Planck-Institut für Chemische Physik fester Stoffe, 01187 Dresden, Germany
| | - Yuri Grin
- Max-Planck-Institut für Chemische Physik fester Stoffe, 01187 Dresden, Germany
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14
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AMAL RAJ A. PRESSURE INDUCED STRUCTURAL PHASE TRANSITION AND SUPERCONDUCTIVITY IN TITANIUM METAL. JOURNAL OF THEORETICAL & COMPUTATIONAL CHEMISTRY 2009. [DOI: 10.1142/s0219633609004551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The electronic band structure, density of states, structural phase transition, and superconducting transition temperature under normal and high pressures are reported for titanium ( Ti ). The normal pressure band structure and density of states of hcp- Ti agree well with the previous calculations. The high pressure band structure exhibits significant deviations from the normal pressure band structure due to s, p → d transition. On the basis of band structure and total energy results obtained using full potential linear muffin-tin orbital method (FP LMTO), we predict a phase transformation sequence of α (hcp) → ω (hexagonal) → γ (distorted hcp) → β (bcc) in titanium under pressure. From our analysis we predict a δ (distorted bcc) phase which is not stable at any high pressures. According to the present calculation, at normal pressure, the superconducting transition of hcp- Ti occurs at 0.36 K which is in agreement with the experimental observation of 0.4 K. When the pressure is increased, it is predicted that, Tc increases at a rate of 3.123 K/Mbar in hcp- Ti . On further increase of pressure Tc begins to decrease at a rate of 1.464 K/Mbar.
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Affiliation(s)
- A. AMAL RAJ
- Department of Chemistry, James College of Engineering and Technology, NavalKadu, Tamil Nadu, India PIN 629852, India
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15
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Yang J, Tse J, Yao Y, Iitaka T. Structural and Electronic Properties of Pristine and Ba-Doped Clathrate-Like Carbon Fullerenes. Angew Chem Int Ed Engl 2007. [DOI: 10.1002/ange.200701555] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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16
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Yang J, Tse JS, Yao Y, Iitaka T. Structural and electronic properties of pristine and Ba-doped clathrate-like carbon fullerenes. Angew Chem Int Ed Engl 2007; 46:6275-7. [PMID: 17634991 DOI: 10.1002/anie.200701555] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Jianjun Yang
- Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, S7N 5E2, Canada.
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17
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Tse JS, Yao Y, Tanaka K. Novel superconductivity in metallic SnH(4) under high pressure. PHYSICAL REVIEW LETTERS 2007; 98:117004. [PMID: 17501079 DOI: 10.1103/physrevlett.98.117004] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2006] [Indexed: 05/15/2023]
Abstract
From first-principles calculations, a high-pressure metallic phase of SnH(4) with a novel layered structure intercalated by "H(2)" units is revealed. This structure is stable at pressure between 70 and 160 GPa. A remarkable feature of this structure is the presence of soft modes in the phonon band structure induced by Fermi surface nesting and Kohn anomalies that lead to very strong electron-phonon coupling. The application of the Allen-Dynes modified McMillan equation with the calculated electron-phonon coupling parameter lambda shows that a superconducting critical temperature close to 80 K can be achieved at 120 GPa.
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Affiliation(s)
- J S Tse
- Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Canada, S7N 5E2.
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18
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Giustino F, Yates JR, Souza I, Cohen ML, Louie SG. Electron-phonon interaction via electronic and lattice Wannier functions: superconductivity in boron-doped diamond reexamined. PHYSICAL REVIEW LETTERS 2007; 98:047005. [PMID: 17358802 DOI: 10.1103/physrevlett.98.047005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2006] [Indexed: 05/14/2023]
Abstract
We present a first-principles technique for investigating the electron-phonon interaction with millions of k points in the Brillouin zone, which exploits the spatial localization of electronic and lattice Wannier functions. We demonstrate the effectiveness of our technique by elucidating the phonon mechanism responsible for superconductivity in boron-doped diamond. Our calculated phonon self-energy and Eliashberg spectral function show that superconductivity cannot be explained without taking into account the finite-wave-vector Fourier components of the vibrational modes introduced by boron, as well as the breaking of the diamond crystal periodicity induced by doping.
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Affiliation(s)
- Feliciano Giustino
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, USA
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